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[en] Coupled-cluster calculations of the static electronic dipole polarizabilities and Cauchy moments are reported for all 15 halomethanes CHmClnF4−m−n. Comparison with available experimental static polarizabilities is made. Excluding three experimental values which seem to be in error, the mean absolute deviation between the CCSD(T) values and experiment is a rather satisfactory 0.5 atomic units for the remaining 11 halomethanes. More experimental work is needed for the polarizabilities of CHCl2F, CCl3F, and CH2Cl2. Additivity approximations work moderately well for α = S(−2) and progressively less well for S(−2k − 2) as k increases.
[en] N,N,N',N'-Tetrabromobenzene-1,3-disulfonamide (TBBDA)/PPh3 and N,N,N',N'-tetrachlorobenzene-1,3-disulfonamide (TCBDA)/PPh3 are two highly reactive reagent systems for the conversion of alcohols corresponding into alkyl chlorides and bromides in moderate to excellent yields in dichloromethane at room temperature under mild and neutral conditions
[en] Highlights: • The shake-off and TS1 processes in the photoionization of the CH2Cl2 are studied. • The fragmentation into two cations dominates the double-photoionization. • The models provide good qualitative description to the experimental data. - Abstract: In this work the roles of the shake-off and knockout processes in the double photoionization of the CH2Cl2 molecule have been studied. The probabilities for both mechanisms accompanying valence-shell photoionization have been estimated as a function of incident photon energy using Samson’s (1990)  and Thomas’s (1994)  models, respectively. The experimental results are in qualitative accord with the models
[en] Highlights: * The sensor 5-bromoindole-3-carboxaldehyde ethylthiosemicarbazone for possesses good selectivity toward Hg2+. * Hg2+ can be extracted and removed from water. * The convenient and efficient Hg2+ test strips based on L were fabricated. A probe based on 5-bromoindole-3-carboxaldehyde ethylthiosemicarbazone (L) was synthesized by a simple and quick one step condensation reaction. L displays a great blue fluorescence in dichloromethane and the fluorescence quenched following Hg2+ coordination. Interestingly, Hg2+ cannot only be detected by this method but also can be extracted and removed from water because dichloromethane and water are immiscible. Moreover, the convenient and efficient Hg2+ test strips based on L were fabricated, which is a potential candidate for the monitoring of Hg2+ in water.
[en] Biodegradation of methylene chloride by a mixed microbial culture, isolated from a common sewage treatment plant, was investigated in a batch system. Batch experiments were performed at room temperature (27 .deg. C) and pH value of 7. The methylene chloride concentration in growth media varied from 25 mgl"−"1 to 250mgl"−"1. A maximum observed degradation was 1 mgl"−"1h"−"1 at 100 mgl"−"1 of methylene chloride. The culture followed substrate inhibition kinetics and specific growth rate were fitted to different substrate inhibition models (Haldane, Aiba and Edwards models) by MATLAB 7.1. Among all models, Haldane was found to better fit with root mean square of 0.947. The biokinetic constants estimated using these models show good potential of the mixed microbial culture in methylene Chloride degradation. Escherichia coli and Staphylococcus aureus are predominant microbes present in the mixed culture
[en] Recently, synthesis of methylenetetrahydrofurans has received much attention due to their versatile usefulness in organic synthesis. The compounds were prepared most frequently either by the Zn(II)/amine-catalyzed coupling reaction of alkylidenemalonates with propargyl alcohol or Michael addition of propargyl alcohol to alkylidenemalonates followed by a palladium-mediated exo-dig cyclization. Methylenetetrahydrofurans can be used for the synthesis of polysubstituted tetrahydrofurans or furans. However, chemical transformations of these valuable compounds were not reported much. Very recently we reported the synthesis of 2,5-dihydrofuran derivatives by the sequential introduction of propargyl alcohol at the primary position of the Baylis-Hillman adducts, radical cyclization, iodolactonization, and finally decarboxylation strategy. During the investigations we reasoned that we could prepare 2,4-disubstituted 2,5-dihydrofuran derivative (B) by following the similar protocol from the methylenetetrahydrofuran
[en] The kinetics of charge-transfer interaction between p-toluidine and iodine in methylene chloride was investigated in depth. The thermal process of formation of the 'inner' complex was found to proceed to an equilibrium. The photochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excited 'outer' complex and the amine ground state. In both cases the same ionic complex (Am2I+I-3, where Am stands for p-toluidine) was detected as the final product. (Author)
[en] Spices and herbs possess antioxidant activity and can be applied for preservation of lipid peroxidation in biological systems. Fenugreek (Trigonella foenum-graecum) is an important spice; its dried seeds have wide application in food and beverages as a flavoring additive as well as in medicines. Crude extracts of fenugreek were prepared by soxhelt extraction method with different solvents such as methanol, ethanol, dichloromethane, acetone, hexane and ethyl acetate. Extracts were subjected for the measurement of total phenolic content (TPC) by Folin-Ciocalteu method as well as flavonoid content, chelating activity, reducing power and antioxidant/radical scavenging activity (1,1-diphenyl-2-picryl-hydrazyl (DPPH degree) free radical scavenging activity). Results from different parameters were in agreement with each other. The results reveal that all extracts of the fenugreek exhibit antioxidant activity. These findings suggest that the fenugreek extracts could act as potent source of antioxidants. (author)
[en] Two simple, rapid and sensitive spectrophotometric methods for the determination of three fluoroquinolones, namely levofloxacin, norfloxacin and ciprofloxacin have been performed either in pure form or in their tablets. In the first method, levofloxacin and norfloxacin are directly treated with bromocresol green (BCG) in dichloromethane while ciprofloxacin is allowed to react with the same dye in aqueous acidic buffer. Highly yellow colored complex species were formed instantaneously in case of levofloxacin and norfloxacin or after extraction into dichloromethane for ciprofloxacin. The formed complexes are quantified spectrophotometrically at their absorption maxima at 411 nm for levofloxacin and 412 nm for norfloxacin and ciprofloxacin. The second method involves the reaction of levofloxacin with ρ-chloranilic acid (ρ-CA) and norfloxacin with tetracyanoethylene (TCNE) in acetonitrile to give complexes with maximum absorbance at 521 and 333 nm for the two drugs, respectively. Adopting the first procedure, calibration graphs were linear over the range 1- 20 μg mL.1 with mean percentage recoveries of 100.41 ± 0.72, 99.99 ± 0.54 and 100.23 ± 0.91 for the three drugs, respectively. For the second procedure, the concentration ranges were 15-250 μg mL.1 for levofloxacin using ρ-CA and 0.8-16 μg mL.1 for norfloxacin using TCNE with mean percentage recoveries of 99.88 ± 0.45 and 100.26 ± 0.68 for the two drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and the results compared favorably to that of reference methods. The proposed methods are recommended for quality control and routine analysis